Strange infestation on orthocone shell, Mississipian, NE England

[TqB]

45 minutes ago, Al Dente said:

Are you 100% sure this is a nautiloid? Some eurypterids have textured cuticle.

 

An intriguing suggestion which would be a first for the area! I can see a couple of cameral walls quite clearly though so sadly probably not... 

[abyssunder]

16 minutes ago, WhodamanHD said:

And what is this? Some sort of bacterial endolith?

document paywalled...

[TqB]

18 minutes ago, abyssunder said:

similar?...

 

image from P. D. Taylor et al. 2013. Endolithic biota of belemnites from the Early Cretaceous Speeton Clay Formation of North Yorkshire, UK. Proceedings of the Yorkshire Geological Society 59 (4): 227-245

 

There are certainly similarities - I have that paper and it says that the haloes are thin planar extensions of the borings along the belemnite laminae. The actual borings are anonymous in this case but haloes occur around different types.:

"Halo structures observed around the Speeton borings appear to penetrate the thin organic-rich laminae of the guards and represent localized dissolution of these layers. The timing of this dissolution is uncertain. One possibility is that it occurred concur- rently with boring, by ‘leakage’ of the demineralizing fluids pro- duced by the endoliths laterally along organic-rich laminae. A second is that the haloes were formed during diagenesis, with the empty borings acting as conduits along which pore waters could attack the organic-rich laminae of the belemnite guard. Further research is needed to discriminate between these two options."

[abyssunder]

I thought that the haloes were formed during diagenesis, now seeing the opinion of the authors, it makes sense. Thank you for the details, Tarquin.
It looks that some of the circular surface structures of your specimen are nicely alligned in rows, others are grouped in a denser population in some areas.

[dalmayshun]

whole thing is so interesting, I love it when the conundrums aren't easily solved, because I learn so much. I wanted to hit that old sharks tooth emoi on each answer. Great job everyone, and great find. 

[Plantguy]

Hi Tarquin, I'm fascinated as well with your find/thread--quite intriguing! Made me go look at some much more recent borings and oolitic material I have---I didnt see anything that close in comparison. Looking forward to hearing/seeing more on this thread and an eventual ID. Very cool!

Regards, Chris 

[fifbrindacier]

On 03/10/2017 at 6:29 PM, FossilDAWG said:

That belemnite might be bored, but it certainly isn't boring.  It's quite beautiful in fact.

 

Don

[TqB]

12 hours ago, abyssunder said:

I thought that the haloes were formed during diagenesis, now seeing the opinion of the authors, it makes sense. Thank you for the details, Tarquin.
It looks that some of the circular surface structures of your specimen are nicely alligned in rows, others are grouped in a denser population in some areas.

I hadn't noticed that, thanks!

 

11 hours ago, dalmayshun said:

whole thing is so interesting, I love it when the conundrums aren't easily solved, because I learn so much. I wanted to hit that old sharks tooth emoi on each answer. Great job everyone, and great find. 

Thanks, I agree! Unknowns are my favourite fossils.

 

9 hours ago, Plantguy said:

Hi Tarquin, I'm fascinated as well with your find/thread--quite intriguing! Made me go look at some much more recent borings and oolitic material I have---I didnt see anything that close in comparison. Looking forward to hearing/seeing more on this thread and an eventual ID. Very cool!

Regards, Chris 

Thanks, Chris, glad it made you look! I hunt with magnification at the original site which is my top one for weird and wonderful, hope another of these turns up soon.

[Spongy Joe]

The big question here, I think, is what was filling the holes if they were borings? The overlapping ones pointed out by Missourian show that there was a plug of something solid, since the outline of one is visible cutting the other. The pyritisation is almost certainly secondary (since only one living species--a gastropod at hydrothermal vents*-- is known to secret pyrite today), and selective pyritisation is most commonly a replacement of silica or organic material, but can affect calcite or other materials as well.

 

Silica would fit with clionid sponges, except that we should see small monaxon spicules within the pyrite, rather than a solid mass (and I certainly don't see spicules in mine either). Also, a sponge bores in order to put a large chunk of itself into protected spaces like galleries inside the shell, which doesn't seem to be happening here. Most likely, then, is that it was something that etched through the shell in order to use it as an anchor, and filled the space with a relatively robust organic material (perhaps something like chitin).

 

If it's organic, that leads to more problems, though... As an example, an entoproct has a muscular foot and attachment disc, and it's possible that some of these began to bore into carbonate (chemically, not physically!). Boring through organic material, however, would be impossible, since you need entirely different solvents...

 

I think we need more info. I don't suppose you could break off a tiny bit of the affected shell to experiment with? Wetting it (or the whole piece, if the pyrite is stable...; if oxidation is an issue, you can immerse in ethanol--or vodka!--instead) and imaging microscopically would tell is more about the distribution of pyrite through the structure, especially in cross section, but embedding a small piece in resin and getting a thin section made would be really interesting.

 

Worth putting some effort in, I think!

 

 

 

 

*for anyone interested: https://en.wikipedia.org/wiki/Scaly-foot_gastropod

[TqB]

@Spongy Joe Thanks for the clear thinking and encouragement, Joe!

 

I'll see what I can do, I've got a better lens now but not a microscope camera. 

Here's the bit of shell that's just worn through to the middle that I photographed badly before, wetted  (have to be v. careful as this stuff falls apart) . We have clear rings, and possible galleries! 

 

The patch of shell is about 2.5mm across, the rings being about 0.3 - 0.4mm.

 

 

 

[Spongy Joe]

Bingo! So it is basically rings, and (as far as memory serves) exactly like my one from the Silurian!

 

Now, what on Earth is it?!?

 

I've got to say, that despite earlier doubts, I think I can see a hint of spicules in there (white arrows). I've got a specimen of a cockle back home with internal galleries complete with sponge remains, and it does have extremely fine spicules. Looking up modern clionids, 0.2 mm long seems to be normal for the largest spicules (e.g. http://aquaticcommons.org/2919/1/44_Old_BoringSponges.pdf), which is at least the right ballpark. If it really is clionid, then we do need something in the way of galleries, and yes, there is indeed a hint of them there as we ll (yellow arrows). I'm guessing that they didn't secrete so many spicules in those areas, as they weren't needed there, and for that reason we're not seeing the same level of pyritisation as in the entry rings.

 

So, yes... it really is looking like a clionid sponge of some sort, but quite possibly a new one. Will have to check mine again very carefully in a couple of months... but if it works out, do you fancy a joint paper?

[TqB]

That would be fun, Joe, but you can do the hard bits of course.  You're very welcome to the specimen anyway if it's worthwhile.

 

Looking at other photos I've just done, I'm not sure about the spicules, they may just be artefacts of the photo at its limits. Obviously needs a decent microscope.

 

Here's a shot centred on the ring you arrowed for them, with different camera settings (and yes, a bit of shell has floated away between shots! - there's plenty more unworn to play with though.)

 

[Spongy Joe]

Botheration! Yes, that clearly is an artefact after all - just goes to show how even pictures can be seriously misleading..!

The 'galleries' still appear to be there, but they're a lot less diagnostic, especially in a recrystallised shell. The plot thickens...

 

I will just add for the moment that the pyrite grains look like framboids, which are a common replacement of soft tissues (i.e. organic matter decaying around the oxic-anoxic boundary). That would be consistent with sponge soft tissue remnants (but in that case, where are the spicules..?), or some other relatively labile organic remains. Which leads us back the same problems of a few posts ago: how can they intersect each other, if there's organic material in the space?

 

What a fabulous puzzle.

[abyssunder]

I wouldn't be surprised if that is Entobia. The more I look, there more I believe is that.

 

picture from here

 

[TqB]

23 minutes ago, abyssunder said:

I wouldn't be surprised if that is Entobia. The more I look, there more I believe is that.

 

 

picture from here

 

Looks very comparable, good example - now we just need to find spicules!

 

By the way, kudos to @Bullsnake for the original suggestion of sponge borings - it may yet turn out wrong but it's a strong contender. 

[abyssunder]

I'm almost sure about the sponge borings. The arrangement of the borings, densly grouped or alligned in rows, is characteristic to clionaid sponge borings.

[GeschWhat]

I could be mistaken, but I think I read about similar features a while back on baculites? Now if I could just remember where I saw it. 

[GeschWhat]

I did a quick google search. I don't think this is the baculite paper I was thinking of, but it does discuss the pitting.

[TqB]

28 minutes ago, GeschWhat said:

I did a quick google search. I don't think this is the baculite paper I was thinking of, but it does discuss the pitting.

Very interesting paper, thanks - I see that the pits are of uncertain origin again, and apparently just on the internal mould so they're attachments for something growing inwards from the internal shell wall.

 

Mine seem to be mainly mining within the shell itself.

 

 

 

[Peat Burns]

Brainstorming a little bit and certainly not ruling out boring sponge as a possible candidate.  Just throwing this out there for consideration and further research.

 

Encrusting foraminifera?

 

Encrusting alga?

[TqB]

23 minutes ago, Peat Burns said:

Brainstorming a little bit and certainly not ruling out boring sponge as a possible candidate.  Just throwing this out there for consideration and further research.

 

Encrusting foraminifera?

 

Encrusting alga?

 

Thanks and keep them coming! I don't know if either of those would produce circular cavities inside the shell?

[Peat Burns]

18 minutes ago, TqB said:

Thanks and keep them coming! I don't know if either of those would produce circular cavities inside the shell?

If it was not exposed to high intensity light, that would rule out the algae.  But I know from experience that encrusting algae can etch glass. 

 

I'm not familiar enough with the encrusting  forams to know the extent to which they can dissolve attachment surfaces.